JP5310120B2 - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein limit of change speed is needed since effect on a combustion state is large at the time of cold engine if intake valve open timing IVO is changed by a variable valve gear, and that combustion state is transitionally deteriorated or duration for reaching a target gets longer in former examples in which change speeds are fixed. <P>SOLUTION: As shown in Fig.(b), a change speed upper limit value is set to a relatively low speed in an angle range where a change quantity of a remaining gas ratio per unit change angle of an intake valve open timing IVO is large and to a relatively high speed in an angle range where the change quantity is small according to an actual intake valve open timing rIVO at that time. Consequently, the intake valve open timing rIVO changes as shown in Fig.(a), and duration for reaching the target intake valve open timing tIVO is minimized while avoiding transitional deterioration of combustion state. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a control device for an internal combustion engine provided with a variable valve gear that makes a valve overlap variable.

  It is known to variably control the valve overlap according to the engine operating conditions by using a variable valve system that can change the intake valve opening timing. There are various types of variable valve operating devices. For example, as disclosed in Patent Document 1, a phase variable mechanism that delays the phase of the camshaft relative to the crankshaft is disclosed in Patent Document 1. There are known types that increase or decrease the working angle.

  Patent Document 3 discloses a technique for enlarging the valve overlap when the engine is cold, increasing the residual gas, and promoting the vaporization of fuel by the heat in order to promote warm-up of the internal combustion engine. ing.

JP 2002-317610 A JP 2002-256905 A JP-A-5-215011

  For example, in an intake port injection type fuel injection device that injects fuel toward the intake port, the temperature of the inner wall of the intake port is low when the engine is cold, so that the atomization of the fuel deteriorates and the fuel wall flow increases. Under such circumstances, when the valve overlap increases, the residual gas in the combustion chamber returns to the intake port, and the fuel atomization is promoted by the heat, so that the combustion state changes. Further, when the wall flow suddenly vaporizes, a transient air-fuel ratio change also occurs. In addition, the actual compression ratio changes as the intake valve opening timing changes.

  That is, when the valve overlap changes, the combustion state changes due to various factors. Therefore, especially when the valve overlap is changed suddenly during cold operation, there is a problem that the combustion becomes unstable transiently or the exhaust performance deteriorates. In order to operate, it is common to limit the rate of change below a certain rate of change.

  However, if the changing speed is limited to a constant speed, it takes a long time to change until the desired intake valve opening timing when the operating condition changes, which is not preferable.

  The present invention relates to a variable valve operating device that changes the intake valve open timing in order to make the valve overlap with the exhaust valve close timing in accordance with the engine operating conditions, and the intake valve open timing by the variable valve operating device. And a change speed limiting means for limiting the change speed at the time of change, wherein the change speed limit means changes to a target change speed according to the control position of the variable valve gear. It is characterized by controlling the speed.

Then, the target rate of change in the change amount is large angular region of the residual gas ratio of unit change angle per intake valve opening timing relative to the low speed, relatively high speed in the above variation is small angular region Is set.

  In other words, when the intake valve opening timing and thus the valve overlap change, the residual gas mainly increases or decreases, and the combustion state changes, but this influence on the combustion state is caused when the intake valve opening timing is delayed. In addition, it does not necessarily occur uniformly, but the influence on the combustion state is relatively large in a certain angle range, and the influence on the combustion state is relatively small in a certain angle range. Therefore, in consideration of such a tendency, the target intake valve opening timing can be reduced in a minimum amount of time while suppressing the influence on the combustion state by controlling the target change speed according to the control position of the variable valve operating device. Can vary up to.

  According to the present invention, when the target control position of the variable valve apparatus changes, the time required to reach the target intake valve opening timing while suppressing the influence on the combustion state due to the change of the valve overlap. Can be shortened.

The system block diagram of the control apparatus of the internal combustion engine which concerns on this invention. The flowchart which shows the flow of the process of a change speed restriction | limiting in this Example. The characteristic view which shows the correlation with the control position of a variable valve apparatus and the oxygen concentration in exhaust_gas | exhaustion. It is a time chart at the time of performing change speed restriction in this example, and shows (a) intake valve opening timing IVO, (b) change speed restriction value, and (c) in-cylinder residual gas ratio.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a system configuration of an internal combustion engine according to the present invention. The internal combustion engine 1 has an intake valve 3 and an exhaust valve 4, and serves as a variable valve operating device 5 for the intake valve 3. In addition, a phase variable mechanism (VTC) for simultaneously delaying both the opening timing and closing timing of the intake valve 3 is provided. This phase variable mechanism is a known configuration that delays the phase of the intake camshaft with respect to the crankshaft, as in Patent Document 1, for example, and continuously adjusts the phase of the valve lift characteristic with respect to the crank angle. Can be changed. The intake passage 7 is provided with an electronically controlled throttle valve 2 whose opening degree is controlled by an actuator such as a motor. These variable valve gear 5 and electronically controlled throttle valve 2 are controlled by a control unit 10.

  A fuel injection valve 8 for injecting fuel into the intake port is disposed in the intake passage 7, and an amount of fuel corresponding to the intake air amount is injected from the fuel injection valve 8.

  The control unit 10 includes an accelerator opening signal APO from an accelerator opening sensor 11 provided on an accelerator pedal operated by a driver, an engine rotation speed signal Ne from an engine rotation speed sensor 12, and an intake air amount sensor. An intake air amount signal from 13, a coolant temperature signal Tw from the water temperature sensor 14, and the like are input. Based on these signals, the control unit 10 performs fuel injection amount, fuel injection timing, ignition timing, throttle valve opening. The control target position of the variable valve gear 5 (in other words, the target intake valve opening timing) is calculated to control the fuel injection valve 8, the spark plug 9, the throttle valve 2, the variable valve gear 5, etc. . If necessary, a sensor for directly detecting the control position of the variable valve apparatus 5, that is, the phase of the camshaft (not shown) may be provided. Alternatively, other detection signals may be used to detect the camshaft phase or intake valve opening timing.

  In the present invention, the variable valve operating device 5 may be any variable valve operating device capable of delaying at least the opening timing of the intake valve 3, and various types of variable valve operating devices can be used.

  Next, the speed limit of the variable valve operating apparatus 5 during cold, which is a main part of the present invention, will be described.

  FIG. 2 shows a flow chart for limiting the speed. In step 1, the target intake valve opening timing tIVO and the actual intake valve set according to the operating conditions at that time by another routine (not shown) are shown. Read the opening time rIVO. When the operating condition changes, the target intake valve opening timing tIVO changes stepwise. In step 2, based on the intake valve opening timing rIVO at that time, the change speed upper limit value is sequentially set along predetermined characteristics. In step 3, the corrected target intake valve opening timing hIVO is sequentially output using the change speed upper limit value so that the change speed of the intake valve opening timing IVO is equal to or lower than the change speed upper limit value. The variable valve gear 5 changes following the corrected target intake valve opening timing hIVO.

  FIG. 3 is a characteristic diagram showing the effect of valve overlap on residual gas during cold weather. The vertical axis represents the percentage of residual oxygen in the exhaust, which alternatively represents the percentage of residual gas in the cylinder. In other words, it can be said that the combustion stability is shown. The horizontal axis indicates the amount of change (crank angle) from the reference position of the variable valve gear 5 to the retard side, and the “10 °” position in the figure is the “overlap 0 °” position. Generally corresponds. Accordingly, the left side of the figure is a minus overlap, and the overlap becomes larger toward the right side of the figure. As shown by the line a in the figure, during cold, the residual oxygen rapidly decreases when the valve overlap reaches a certain size. Line b indicates the exhaust air-fuel ratio, and the exhaust air-fuel ratio is substantially constant as shown in the figure. Point c1 is a characteristic when the water temperature is 40 ° C., and c2 is a characteristic when the water temperature is 86 ° C.

  As shown in FIG. 3, when the valve overlap is changed by the variable valve apparatus 5, the combustion state changes greatly in a certain angle range, and the combustion state does not change much in a certain angle range. Accordingly, in step 2 of FIG. 2, the change speed upper limit value is set in consideration of such a tendency. In other words, the change rate of the residual gas ratio per unit change angle of the intake valve opening timing is relatively low in an angle region, relatively high in an angle region where the change amount is small, and the change speed upper limit value is Is set.

  FIG. 4 is a time chart showing the behavior when the target intake valve opening timing tIVO changes stepwise due to changes in engine operating conditions and the like. (A) Change in intake valve opening timing IVO and (b) Step 2 (C) shows the change in the upper limit value of the change speed, which is sequentially set, and (c) the change in the residual gas ratio in the cylinder. Further, the characteristics of the conventional example in which the change rate is limited to a constant value are also described. As shown in this time chart, when the target intake valve opening timing tIVO changes stepwise, the corrected target intake valve opening timing hIVO and the actual intake valve opening timing rIVO following the target intake valve opening timing tIVO gradually change. In particular, based on the actual intake valve opening timing rIVO that sequentially changes, the upper limit value of the change speed changes as shown in (b), and the intake valve opening timing rIVO is relatively moderate in an angular region where the combustion state is likely to change. To change. Thereby, it is possible to quickly change to the target intake valve opening timing tIVO in a minimum time without incurring a transient deterioration of the combustion state.

  In the conventional example of FIG. 4, since the change speed is given relatively large, the timing of reaching the target intake valve opening timing tIVO as in (a) is not different from that in the embodiment, but is clear in (c). Thus, the residual gas ratio changes rapidly during the change, and the influence on the combustion state is great. If the change in the residual gas ratio is gradually changed in this angular region as in the embodiment, the timing for reaching the target intake valve opening timing tIVO is delayed from that in the embodiment.

  After the engine is warmed up, the influence on the combustion state due to the vaporization of the fuel becomes small. Therefore, the limitation on the change speed as described above is limited when the engine is cold (for example, the water temperature, the oil temperature, etc. Only).

DESCRIPTION OF SYMBOLS 3 ... Intake valve 5 ... Variable valve operating apparatus 8 ... Fuel injection valve 10 ... Control unit 14 ... Water temperature sensor

Claims (4)

A variable valve gear that changes the intake valve opening timing in order to make the valve overlap between the exhaust valve closing timing and the engine operating conditions,
A change speed limiting means for limiting the change speed when the intake valve opening timing is changed by the variable valve operating device;
In a control device for an internal combustion engine comprising:
The change speed limiting means controls the change speed to a target change speed according to a control position of the variable valve operating device ,
The target change speed is set to a relatively low speed in an angle region where the change amount of the residual gas ratio per unit change angle of the intake valve opening timing is large, and to a relatively high speed in an angle region where the change amount is small. control apparatus for an internal combustion engine, characterized in that it is.   2. The control device for an internal combustion engine according to claim 1, wherein the internal combustion engine includes a fuel injection valve that injects and supplies fuel toward an intake port as a fuel supply device.   3. The control apparatus for an internal combustion engine according to claim 1, wherein the change speed is limited by the change speed limiting means only when the engine is cold. The control apparatus for an internal combustion engine according to any one of claims 1 to 3 , wherein the variable valve mechanism comprises a phase variable mechanism that retards the valve lift characteristic with respect to the crank angle.

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